Papers by Keyword: PTFE

Abstract: Hydro turbines are the key features of the developing globe for utilizing one of the important renewable energies, namely hydro power. The longevity of these hydro machineries links directly to the surface properties of critical component like impellers, as these components are exposed to slurry and cavitation erosion during their use and should be addressed by the properly designed material surfaces for consistent efficiency. The surface properties can be altered and improved by developing coating in conventional steels that are used for impellers. A recommended hard coating for such applications involves titanium carbide (TiC) with Ni and Cr binders. Along with hardness, an increase in surface hydrophobicity can also reduce wear. High velocity oxygen fuel (HVOF) spraying process comes under the umbrella of thermal spray process that utilizes melting of powders via burning of fuel and these molten powders were bombarded on the surface with supersonic velocity to generate a coating. In this paper, HVOF thermal sprayed coating consisting of TiC and NiCr has been utilized for SS410 steel. In addition, a thin layer of polytetrafluoroethylene (PTFE) has also been investigated on the HVOF sprayed surface to enhance its hydrophobicity. The developed surface has been characterized by static contact angle, hardness, porosity, surface roughness, and coating thickness. Variable impingement parameters, namely sand concentration (20000 & 40000 ppm), angle of impingement (45 & 90°) for slurry testing, stand-off-distance (4 & 8 cm), and flow velocity (15 and 30 m/sec) for cavitation testing were opted for analysis the wear resistance of candidate specimens. From the results, it has been observed that the implementation of a PTFE layer leads to super hydrophobicity. However, the hardness and surface roughness have been reduced with the assistance of PTFE layer. Meanwhile, the slurry and cavitation erosion resistance were also found to be improved by the PTFE layer due to the increase in static contact angle. In the case of cavitation erosion, maximum jet velocity and stand-off distance contribute to more wear, owing to sufficient bubble generation. Next, in case of slurry erosion testing, mixed aspect of erosion wear with respect of influence of parameters was observed for coated and uncoated samples. Ductile mode of failure was observed for SS410, and PTFE sprayed specimens, on the other side, HVOF sprayed TiC+50%NiCr coating showed mixed mode of erosion.

Abstract: Start-stop rolling contact fatigue tests of PEEK-PTFE hybrid radial bearings were carried out, to investigate the influence of start-stop heat cycle on the friction coefficient of PEEK-PTFE hybrid radial bearings. It was found in all start-stop tests, the temperature of sample side increased as the friction coefficient increased. RCF cycles to reach 50 °C of the third start-stop phase clearly increased from the second start-stop tests, and then kept constant value.

Abstract: Nitrogen-doped TiO₂ (N-TiO₂)/polytetrafluoroethylene (PTFE) has been prepared by optimization of nitrogen and polytetrafluoroethylene. N-TiO₂ has been modified by optimizing doping concentration in two-step process synthesis via solvothermal treatment, by mixing TiO₂ and variation ammonium carbonate as a nitrogen source at 0.5 M, 1.0 M, 1.5 M. Synthesized materials denoted as N-TiO₂, were characterized by X-Ray Diffraction (XRD), Fourier Transform Infrared ( FTIR), Scanning Electron microscopy (SEM), and spectrophotometer UV Vis. Based on the XRD pattern, a shift diffraction pattern was assigned to [101] that indicated the nitrogen successfully doped. The functional group identified by FTIR shown an O-Ti-N bond seems to influence the energy gap of TiO₂. The presence of nitrogen as an impurity in semiconductor TiO₂ was decreased the amount of bandgap energy from 3.10 eV to 2.95 eV. Synthesized N-TiO₂ is a nanosphere morphology. Glass substrate containing N-TiO₂/PTFE has excellent self-cleaning in a ratio N-TiO₂/PTFE (1:3) and based on optical properties, show that each coating on the glass substrate has high transmittance for composition N-TiO₂/PTFE (1:3) > 90%. The contact angle before and after oleic acid contaminant under visible light are 97.68 and 94.16º, respectively. The discoloration of methylene blue (MB) coated on the glass performed under visible light shown 60.32% degradation.

Abstract: Polytetrafluoroethylene (PTFE) lubricant is commonly applied for dry contact due to its low friction properties. However, low strength properties can lead to short service-life due to high wear rate, especially under high contact load. The method to add PTFE into a solid contact during operation as a transfer layer has been one of the major attempts in this field. This study aims to investigate the influence of operating parameters, i.e., revolution cycle, sliding speed and applied load, on coverage area of transfer PTFE on the bearing steel (AISI 52100) disc. The experiments were performed on the modified pin-on-disc apparatus using a unidirectional ground disc. The areas with disc grinding direction parallel (parallel morphology) and perpendicular (perpendicular morphology) to the pin sliding direction were both examined. The ascending of transfer coverage area with an increasing revolution cycle within the first 1000 cycle was observed on the area with a sliding direction perpendicular to the disc grinding direction while the descending of transfer coverage area was found on the parallel case. The further increase in the revolution cycle led to only a small change in the transfer coverage area. With more revolution cycles, the pin wear rate increased as a decrease in transfer coverage area formed on the counter-face. Research suggested that the amount of transfer coverage area decreased with increasing sliding speed. However, it could be increased by increasing the applied load.

Abstract: In the present work, dry sliding wear characteristics of polytetrafluoroethylene (PTFE) composite reinforced with 35% by weight carbon fiber against AISI 304 stainless steel counterface is investigated with a view to consider PTFE composite as an alternative material for automotive applications. Dry sliding experiments were performed on pin-on-disk wear testing machine varying the normal load on pin, disk rotation (rpm) and temperature correlating with the range of pressure, sliding velocity and temperature variation at reciprocating conditions of compressor. A mathematical model to predict specific wear rate in terms of pressure and temperature was developed to understand parametric effect on wear rate. Specific wear rate has been observed to decrease with increase in pressure and temperature. Although, pressure (normal load) has been observed as more significant in lowering specific wear rate than temperature, no significant benefit was observed at higher ranges of pressure. Decrease in specific wear rate with increase in normal load (pressure) can be attributed to formation of transfer film at sliding interfaces. However, it is necessary to characterize transition of formation of transfer film varying with normal load and temperature respectively.

Abstract: In this paper, in order to investigate friction coefficient and wear of PEEK-PTFE hybrid radial bearings, rolling contact fatigue tests were performed under radial loads ranging from 93N to 387N at 600rpm in dry conditions. It was found that friction coefficients were 0.013 to 0.032 throughout the tests. Operation temperature followed the change in the friction coefficient, and PEEK-PTFE radial ball bearings exhibited stable performance even though the temperature locally approached 100 °C due to frictional heat. Moreover, wear loss of bearing components excluding alumina balls increased exponentially with increase of load.

Abstract: The paper introduces the research background, current status and performance of architectural membrane materials, analyzes the superiority of PVC and PTFE performance, discusses the aging and standards of architectural membrane materials, and conducts new rheological destruction of architectural membrane materials. The aging and relaxation characteristics described by the constitutive equations, and the viscos-elastoplastic rheological failure of architectural membranes for constitutive experiments. At the end of the thesis, the aging performance degradation of architectural membrane materials is discussed, and the aging of architectural membrane materials and the significance of membrane performance degradation are explored in depth.

Abstract: This study provides an overview of the effects of prolonged acid attack on the surface of PTFE gaskets, assessed using Fourier Transform Infrared Spectroscopy (FT-IR), Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC). The PTFE analysed originates from two manufacturers in form of Teflon adhesive tapes, used as gaskets in an ultrasonic tyre moulds cleaning plant (UMCS). The gaskets were exposed to various acid baths, temperature and ultrasonic waves, and shown anomalous damage and surface degradation in a relatively short operation time. The analyses here reported have been aimed at investigating this unusual behaviour. PTFE samples have been treated with different acid mixes to evaluate possible different aging effects. Both surface and core have been analysed after aging, providing evidence of the degradation phenomena. In particular, different acid treatments have highlighted different response of PTFE and differences among manufacturers.

Abstract: The aim of this paper is to obtain the Cu-Sn-PTFE composite coating with wear-resistant and antifriction properties, which can improve the comprehensive performance of Cu-Sn coating and satisfy the self-lubricating property in special working condition. This coating was prepared by pulse current on the basis of non-cyanide pyrophosphate-stannate Cu-Sn plating bath. The effect of PTFE content on the microstructure, composition, microhardness, and tribological properties were analyzed and compared in detail. Results show that with appropriate PTFE content, the composite coating of Cu-Sn-PTFE displays preferable low friction and anti-wear behavior.

Abstract: Polytetrafluoroethylene (PTFE) powder is used as a solid lubricant in commercial antifriction coatings. However, most of the matrix polymers are usually not compatible with virgin PTFE resulting in low dispersion and mechanical film stability and adhesion. In our research PTFE TF 2025 was irradiated by g-beam generating PTFE micropowder with persistant radicals and functional groups. These functional groups are able to perform a chemical grafting (cg) of polyamideimide (PAI) and modified PTFE-micropowder by reactive extrusion in melt. Based on grinded extrudates PAI-PTFE-cg dispersions were formulated followed by characterizing dispersion as well as film properties. It was found, that PAI-PTFE-cg dispersion comprises very small PTFE-particles at higher g-irradiation doses in homogeneous dispersions. In addition, all samples showed outstanding film flexibility. Basic tribological properties under mixed lubrication were studied by using a ring-on-disk tribometer. Finally, diluted dispersions were applied to a multi-surface sliding bearing (four segments) for testing in a hydrodynamic plain test bench.